Excerpts from mail--- via tor-relays's message of June 22, 2024 5:14 pm: > Hi o/, > > During the Tor Operator Meetup I asked about Quick Assist Technology (QAT) > support and was asked to bring it to the tor-relays mailing list so the > network team can take a look at the question. > > In 2025 we're going to build one or more new servers and we're looking in to > optimizing the performance per watt ratio since some of our current servers > are rather power hungry ;-). > > I'm wondering whether QAT works for Tor to offload compression, hashing and > encryption. In theory, looking at the nature of Tor (a lot encryption), this > could result in a huge performance boost of 100-300% (based on other hashing, > cryptographic and compression offload benchmarks). Support for QAT also has > improved considerably over the years so many programs/workloads already work > nicely with it, but I'm not sure about Tor. > > It looks like Tor uses [1] RSA-1024, AES-CBC, AES-CTR, Curve25519, Ed25519, > SHA1, AES256, AES3-256. Most (no Curve- and Ed25519) should in theory also > work with QAT [2] (although I guess only a few would impact performance > significantly when offloaded). But the question is: does it really work? If > not, what would be needed to make it work? Are there Tor operators who > already utilize QAT? Does the Network Team have some insight in to this? :) > > Some of the potential advantages when comparing a similar amount of traffic: > - Lower power consumption (much cheaper to run in expensive European > countries). > - Less CPU cycles required (= cheaper CPUs). > - Less heat/cooling required (easier to put in distribution boxes and other > small places). > - Smaller physical footprint (easier to put in distribution boxes and other > small places). > - Alleviates some of the issues and challenges caused by Tor's single > threaded architecture by effectively increasing bandwidth per CPU core > considerably. > > With regards, > > tornth > > [1] > https://spec.torproject.org/tor-spec/preliminaries.html?highlight=cipher#ciphers > [2] > https://www.intel.com/content/www/us/en/support/articles/000093843/technologies/intel-quickassist-technology-intel-qat.html > > _______________________________________________ > tor-relays mailing list > [email protected] > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays >
I previously answered this at https://lists.torproject.org/pipermail/tor-relays/2022-April/020495.html. In principle, it should work if you set HardwareAccel 1. However, based on my profiling, the actual AES encryption doesn't use that much CPU when using regular AES instructions. I couldn't find any independent QAT benchmarks from an internet search, but https://calomel.org/aesni_ssl_performance.html says AES-NI can reach over 1 GB/s per core, which is far more than Tor can use. Cheers, Alex. _______________________________________________ tor-relays mailing list [email protected] https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays
